Models 20, 22, 24, 25, 26 fall into a category of mechanisms that Reuleaux called power escapements. Escapements in clocks regulate small amounts of energy to keep the pendulum swinging (e.g., see model X-3). Power escapements regulate the motion of larger energy systems. Reuleaux seems to have designed these models as analogs to dynamic regulators, such as the rotating balls of Wattâs speed regulator in steam engines. Reuleaux gave only one description of a power escapement for model N-26 in The Constructor. However, he does not give a direct application of these mechanisms. Neither do they appear in later treatises or more modern model collections. Perhaps one can call them âthe mystery mechanismsâ.

This model is an extremely complex mechanism whose motions are governed by the dynamic laws of Newton. Two cylindrical weights are attached to two pulley wheels. The smaller weight is used to return the lever to its starting position. The other larger weight represents the force or potential energy whose motion is regulated by the escapement. In operation, the larger weight is lowered automatically as the lever and inverted pendula oscillate back and forth and up and down respectively (see video). Part of the motion is also controlled with dry friction slides on the model. The use of a power escapement of the verge and foliet type (model X-1) for speed control of a water pump can be seen in the 17th century machine compendium of Jacob de Strada.